Test head vertical support system

ABSTRACT

A manipulator for translating a load along an axis of translation is provided. The manipulator comprises an outer column and a telescoping column positioned adjacent the outer column. The telescoping column is attached to the load and configured to translate the load along the axis of translation. At least one guiding member is mounted between the outer column and the telescoping column, wherein the guiding member is configured to guide the telescoping column as the telescoping column translates along the axis of translation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/521,461, filed Jun. 26, 2009, which is a 371 of PCT InternationalApplication No. PCT/US2007/026306, filed Dec. 26, 2007, which claimspriority under 35 U.S.C. §119 to U.S. Provisional Patent ApplicationSer. No. 60/877,915, filed Dec. 29, 2006, and U.S. Provisional PatentApplication Ser. No. 60/971,104, filed Sep. 10, 2007. All aboveapplications are incorporated fully herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of art of test headpositioners for automatic integrated circuit (IC) testing equipment.

BACKGROUND OF THE INVENTION

Automatic test equipment (ATE) for integrated circuits (ICs) has beendeveloped to facilitate electrical testing of IC's at selected stages ofthe IC manufacturing process. Such ATE often includes a test head whichmust be manipulated into a docked position with a testing peripheralusing a test head positioner (or manipulator). Test head positioners aregenerally described, for example, in U.S. Pat. Nos. 6,911,816,6,888,343, 5,608,334, 5,450,766, 5,030,869, 4,893,074 and 4,715,574, andU.S. patent application Ser. No. 10/955,441. Additional publicationswhich are of particular relevance are WIPO publication WO 05015245A2 toChristian Mueller, WO 04031782A1 to Christian Mueller, and U.S. Pat. No.4,705,447 to Nathan R. Smith. All of the foregoing are incorporated byreference in their entirety for their teachings in the field of testhead positioners for automatic test equipment for integrated circuits orother electronic devices.

Briefly, a conventional automatic testing system generally includes aperipheral apparatus for precisely placing and constraining the ICdevice under test (DUT) in a fixed position test site. Also included isa moveable test head for testing the DUT. The peripheral apparatus may,for example, be a wafer prober for testing devices before they areseparated from a silicon wafer or a package handler for positioning andtesting packaged devices. In practice, the test head is translatedand/or rotated about one or more axes and brought into the vicinity ofthe DUT test site included in the peripheral apparatus. Prior todocking, the mating connectors of the test head and the DUT test siteare precisely aligned to avoid damaging any of the fragile electricaland mechanical components. Once docked, test electronics of the testhead transmit signals through various contacts of the DUT and executeparticular test procedures within the DUT. In the course of testing, thetest head receives output signals from the DUT, which are indicative ofits electrical characteristics.

In order to precisely mate the test head with the peripheral apparatus,the test head is optionally capable of movement with all six degrees ofspatial freedom. To facilitate such motion, a test head positionersystem is commonly employed to precisely position the test head withrespect to the peripheral. The test head positioner system may also bereferred to in the art as a test head positioner or a test headmanipulator.

Referring now to the exemplary test head positioner described in U.S.Pat. No. 6,888,343, the test head 502 is coupled to main arm 511, andmain arm 511 is slideably coupled to linear guide rail 510 that extendsvertically along the length of column 545, as best shown in FIGS. 5A and5B. A motor 2416 may be adapted to translate main arm 511 (and test head502) vertically along linear guide rail 510. A counter weight assemblybiases the weight of main arm 511 (and test head 502) in a substantiallyfixed vertical position upon disengagement of the motor. As best shownin FIGS. 23 and 24, motor 2416 is mounted to frame 2422 of column 545,and is indirectly connected to pulley 2421 by timing belt 2420. Pulley2421 is mounted to pulley 2406 by fasteners 2407 (shown in FIG. 23, butnot numbered), such that pulleys 2421 and 2406 rotate simultaneously. Acable 2410 is positioned about pulley 2421. One end of cable 2410 iscoupled to mount 736 of main arm 511 and the opposing end of cable 2410is coupled to a counter balance 2413. In operation, if clutch 2426 ofmotor 2416 is engaged, the motor 2416 rotates pulleys 2406 and 2421,thereby translating the end of cable 2410 that is connected to mount 736along the Y-axis. Thus, the cable 2410 translates the mount 736 of mainarm 511, along with test head 502, in a vertical direction. Once clutch2426 of motor 2416 is disengaged, the counterbalance 2413 suspends mount736 and test head 502, in a substantially fixed vertical position.Furthermore, with clutch 2426 of motor 2416 disengaged, test head 502 isin a substantially weightless condition and may be readily movedvertically with a relatively small externally (manually) applied force.This is known as compliance and it enables an operator to manuallyposition the test head or a docking apparatus to maneuver the test headinto or out of its docked position with a peripheral.

Further, the exemplary test head positioners disclosed in WO 05015245A2,and WO 04031782A1, and U.S. Pat. No. 4,705,447 both support a test headin a substantially-weightless, compliant condition using a pneumaticapparatus rather than counter weights. In WO 05015245A2 and WO04031782A1 a pneumatic controller is provided which, in addition toproviding compliance, automates vertical translation of the test head.

The aforementioned test head positioner systems may be sufficient;nevertheless, there continues to be a need to further improve verticalsupport systems for test heads, in the interest of weight, efficiency,simplicity and cost.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a manipulator for translatinga load along an axis of translation is provided. The manipulatorcomprises an outer column and a telescoping column positioned adjacentwith respect to the outer column. The telescoping column is attached tothe load and configured to translate the load along the axis oftranslation. At least one guiding member is mounted between the outercolumn and the telescoping column, wherein the guiding member isconfigured to guide the telescoping column as the telescoping columntranslates along the axis of translation.

According to another aspect of the invention, a load positioning systemfor translating a load along an axis of translation is provided. Theload positioning system comprises a telescoping column coupled to theload, and a pneumatically operated piston configured to drive thetelescoping column along the axis of translation. The pneumaticallycontrolled unit is configured to raise, lower or substantially maintainthe position of the telescoping column along the axis of translation.

According to another aspect of the invention, a load positioning systemfor translating a load along an axis of translation is provided. Theload positioning system comprises a telescoping column coupled to theload, and a pneumatically operated piston configured to drive thetelescoping column along the axis of translation. The pneumaticallycontrolled unit includes a regulator configured to raise, lower orsubstantially maintain the position of the telescoping column along theaxis of translation based on a pilot pressure received by the regulator.

According to another aspect of the invention, a load positioning systemfor translating a load along an axis of translation is provided. Theload positioning system comprises a telescoping column coupled to theload; a pneumatically operated piston configured to drive thetelescoping column along the axis of translation; and a pneumaticallyoperated brake lock configured to substantially lock the position of thepiston upon engagement of the lock. The brake lock may be furtherconfigured to sense when the load is unbalanced and preventdisengagement of the lock when the load is unbalanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures may be arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1A is a perspective view of a test head manipulator system;

FIG. 1B is another perspective view of the test head manipulator systemof FIG. 1A, wherein the test head is illustrated in an elevatedposition;

FIG. 2A is a partial cut-away perspective view of the pneumaticmanipulator assembly of FIGS. 1A and 1B, whereby the pneumatic controlunit is omitted for the purpose of clarity;

FIG. 2B is another partial cut-away perspective view of the pneumaticmanipulator assembly of FIG. 2A;

FIG. 2C is a perspective view of the pneumatic manipulator assembly ofFIG. 2A, whereby the access panel and column cover are omitted for thepurpose of clarity, and the telescoping column and pneumatic piston rodare illustrated in an elevated position;

FIG. 2D is a perspective view of the pneumatic manipulator assembly ofFIG. 2C, whereby the telescoping column is omitted for the purpose ofclarity;

FIG. 3 is a cross-sectional view of the pneumatic manipulator assemblytaken along the lines 3-3 shown in FIG. 2D;

FIG. 4 is a detailed perspective view of the guiding member assemblyshown in FIG. 3;

FIG. 5 is a free body diagram illustrating the forces acting upon thetest head and pneumatic manipulator assembly, shown schematically;

FIG. 6 is a schematic diagram of a portion of an exemplary pneumaticsystem for controlling movement of the automated testing apparatus;

FIG. 7 is a schematic diagram of a portion of another exemplarypneumatic system for controlling movement of the automated testingapparatus;

FIG. 8 is a schematic diagram of a portion of yet another exemplarypneumatic system for controlling movement of the automated testingapparatus;

FIG. 9 is a schematic diagram of a portion of another exemplarypneumatic system for controlling movement of the automated testingapparatus;

FIG. 10 is a schematic diagram of a portion of another exemplarypneumatic system for controlling movement of the automated testingapparatus;

FIG. 11 is an exploded perspective view of a portion of anotherexemplary pneumatic unit;

FIG. 12 is an assembled perspective view of the pneumatic unit of FIG.11;

FIG. 13 is a cross-sectional view of the pneumatic unit taken along thelines 13-13 shown in FIG. 12; and

FIG. 14 is a schematic diagram of a portion of another exemplarypneumatic system for controlling movement of the automated testingapparatus.

DETAILED DESCRIPTION OF THE INVENTION

The invention will next be illustrated with reference to the figures.Such figures are intended to be illustrative rather than limiting andare included herewith to facilitate explanation of the presentinvention. The figures are not necessarily to scale, and are notintended to serve as engineering drawings. In the figures, the numeralsfollowing the item numbers (e.g., 16(I)) indicate a position ororientation (e.g., position I) of the feature represented by the itemnumber (e.g., item 16).

To be consistent with descriptions of prior art test head positionersystems, a Cartesian coordinate system 100 illustrated in FIGS. 1A, 1B,3 and 5 is used in which a vertical axis (otherwise referred to as aY-axis) is denoted by axis 102, a horizontal axis (otherwise referred toas an X-axis, side-to-side axis or left-right axis) is denoted by axis104, and another horizontal axis (otherwise referred to as a Z-axis orin-out axis) is denoted by axis 106.

Referring now to FIG. 1A, an automated testing apparatus is denoted bynumeral 10. According to this exemplary embodiment, automated testingapparatus 10 comprises a peripheral testing apparatus 30, which may befor example a prober, package handler, device handler, or otherapparatus for placing constraining a DUT (not shown) in a substantiallyfixed position. In the exemplary system shown in FIG. 1A, the exemplaryperipheral shown happens to be a prober. A test head 12 is movablypositioned above peripheral testing apparatus 30 and configured toselectively engage the DUT for testing purposes at various stages of theIC manufacturing process. An articulating arm assembly 14 interconnectsthe test head 12 to a test head manipulator 16. Specifically,articulating arm assembly 14 is fastened to plate 19, which is mountedto a surface of test head manipulator 16. Articulating arm assembly 14includes three segments that are capable of rotation about axes 102 withrespect to each other and which are parallel with axis 102. Therotational capability of the articulating arm assembly 14 isparticularly relevant to the teachings hereinafter. In particular,articulating arm assembly 14 provides three degrees of motion freedom ina horizontal plane that is parallel to X-axis 104 and Z-axis 106. Lowfriction bearings and components are used in constructing arm assembly14 so that compliance is proved in translation in the directions ofX-axis 104 and Z-axis 106 as well as in rotation about axes parallelwith the Y-axis 102. Articulating arm assembly 14 is derived from thepositioner arm assembly described in U.S. Pat. No. 4,705,447. The '447patent also describes alternative arm structures that provide threedegrees of motion freedom in a horizontal plane and which could beadapted to the present invention.

Referring now to FIGS. 1A and 1B, the vertical position of test head 12is controlled by test head manipulator 16. The test head manipulator 16generally comprises a telescoping column 20 positioned within a rigidouter column 22. The telescoping column 20 is positioned to translatealong Y-axis 102 with respect to the fixed outer column 22. The outercolumn 22 is fixedly mounted to a baseplate 27 and is generallyincapable of movement in this exemplary embodiment. However, asdescribed in U.S. Pat. No. 6,888,343, the outer column 22 may beattached to a base assembly which facilitates motion along the X andZ-axes and rotation about the Y-axis. Furthermore, while the illustratedembodiment has the telescoping column member within a fixed outer columnmember, it is also possible to configure the device such that the innermember is fixed and the outer member telescopes relative thereto.

The telescoping column 20 is shown in a retracted position in FIG. 1A,and an extended position in FIG. 1B. In a retracted position oftelescoping column 20, test head 12 is directly adjacent handlingapparatus 30 for testing. In an extended position of telescoping column20, as shown in FIG. 1B, test head 12 is spaced away from handlingapparatus 30.

A fluid-based power source is configured to translate telescoping column20 along the Y-axis 102. In the exemplary embodiment an air-operatedpneumatic power source is preferred; however, it is possible that otherembodiments may utilize gasses other than air or, in certain situations,incompressible liquids. More particularly, in the exemplary embodiment apneumatic control unit 18 mounted to the exterior of outer column 22 isconfigured to supply compressed air to a pneumatic unit 26 (see FIG. 2D)positioned within outer column 22. The pneumatic unit 26 includes apiston that translates in response to the air pressure supplied topneumatic unit 26 by pneumatic control unit 18. The piston is coupled totelescoping column 20 and configured to translate the telescoping column20 along vertical axis 102, as described in greater detail withreference to FIG. 2D.

The pneumatic control unit 18 includes a pressure reducing regulator 24for coupling with a compressed air source (not shown). Although notexplicitly shown, pneumatic control unit 18 includes a second adjustablepressure regulator. By adjusting the pressure setting of the secondpressure regulator, the telescoping column 20 translates upward,downward, or remains in a fixed, compliant position, as will bedescribed hereinafter. When in the fixed, compliant position,telescoping column 20 may be moved vertically upwards or downwards by areasonably low external force, providing test head 12 with verticalcompliance.

Referring now to FIG. 2A, a detailed view of the test head manipulator16 is shown. The test head manipulator 16 is denoted by the Romannumeral “I” in this figure (and FIG. 2B) to signify that the telescopingcolumn 20 is illustrated in a retracted position. In this figure,pneumatic control unit 18 is omitted for the purpose of clarity.

In FIG. 2A, a portion of outer column 22 and manipulator cover 21 arecut away to reveal two guiding member assemblies 32 interposed betweentelescoping column 20 and outer column 22. The test head manipulator 16optionally includes a total of four guiding member assemblies (see FIG.2B). Each guiding member assembly 32 includes two guiding members (forexample, cam followers, rollers, or wheels) that freely rotate abouttheir respective axes to facilitate vertical translation of telescopingcolumn 20 with respect to outer column 22, as best shown in FIG. 4. Theguiding member assemblies 32 are each fixedly mounted to an interiorcorner of outer column 22 by a set of four fasteners 41.

A stabilization leg 34 is fixedly mounted to baseplate 27 of themanipulator 16 by one or more fasteners (one fastener shown). A portionof the weight of test head 12 is distributed over the length ofstabilization leg 34. The stabilization leg 34 limits deflection of testhead manipulator 16 under the weight of the test head 12. A support 43is positioned on the underside of stabilization leg 34 to contact thefloor of the testing facility. Although not shown, the stabilization legmay also be mounted to the floor or mounted to a surface of peripheraltesting apparatus 30 to enhance structural integrity of the manipulator16. Although only one stabilization leg is illustrated, the manipulatormay include any number of stabilization legs required to support theweight of the test head and retain the manipulator in a substantiallyupright position. A support leg 39 is fastened to the underside ofbaseplate 27 for contacting the floor.

A removable access cover 31 is provided on the outer column 22 tofacilitate access to the interior of test head manipulator 16, asexplained in greater detail with reference to FIG. 2B. A cover 21 isfastened over the top open end of outer column 22. The cover 21 limitsdeformation of the top open end of outer column 22 under the weight oftest head 12. As explained in greater detail with reference to free bodydiagram shown in FIG. 5, the weight of test head 12 causes a bendingmoment that is distributed over the length of telescoping column 20.Reaction forces generated by the bending moment are directly applied tothe guiding members. Because guiding members are mounted at or nearbythe top end of outer column 22, as shown, a considerable proportion ofthe force generated by the bending moment is applied to the top end ofouter column 22. The cover 21 is fastened to the top end of outer column22 to limit potential deformation of outer column 22. In addition, cover21 limits dust and debris from settling within the interior of test headmanipulator 16 or interfering with the rotation of the guiding members.

Referring now to FIG. 2B, the access cover 31 is omitted to reveal theentire length of telescoping column 20 and a small segment of thecylinder block of pneumatic unit 26. The pneumatic unit 26 is optionallypositioned within the interior of telescoping column 20 and fixedlymounted to baseplate 27. The pneumatic unit 26 is fluidly connected tothe pressurized air source (not shown), via the pneumatic control unit18, by one or more fluid carrying conduits (not shown). Although notshown in this view, a telescoping piston rod travels within the cylinderblock of pneumatic unit 26. The piston rod is indirectly coupled totelescoping column 20 enabling translation of telescoping column 20along the Y-axis 102, as explained in greater detail with reference toFIG. 2D.

In this view, a portion of outer column 22 is cut-away to reveal fourguiding member assemblies 32 mounted to two opposing interior corners ofouter column 22. A set of two opposing guiding member assemblies 32 arepositioned at the top end of outer column 22, and a second set ofopposing guiding member assemblies 32 are positioned at about themidpoint of the length of outer column 22. The two guiding memberassemblies 32 mounted at the top end of outer column 22, as shown, arepositioned to substantially limit or prevent deflection of telescopingcolumn 20 under the weight of test head 12. Two guiding members 32,positioned at a convenient distance apart to fit the design calculationsalong outer column 22, provide additional support to telescoping column20. Although four guiding member assemblies 32 are included in thisexemplary embodiment, the test head manipulator may include any numberof guiding member assemblies 32. Although four guiding member assemblies32 are shown, it may be desirable in certain situations to include morethan four guiding member assemblies 32. In other situations it may bedesirable to include only two guiding member assemblies 32 at locationssufficient to support the load.

Referring now to FIG. 2C, another detailed view of the test headmanipulator 16 is shown (pneumatic control unit 18 and access cover 31are omitted for clarity). The test head manipulator 16 is denoted by theRoman numeral “II” in this figure (and FIG. 2D) to signify that thetelescoping column 20 is illustrated in an extended position. In thisview, telescoping column 20 is elevated to the extended position,thereby revealing a greater length of the cylinder block of pneumaticunit 26, as compared with FIG. 2B.

A spherical bearing 51 couples horizontal shaft 50 to the dynamic pistonrod (not shown in this view) of pneumatic unit 26. The horizontal shaft50 is mounted through apertures 33 disposed in the upper end oftelescoping column 20. The pneumatic unit 26 and telescoping column 20are interconnected at the interface between the horizontal shaft 50 andapertures 33. Although not shown, horizontal shaft 50 may be mounted toaperture 33 by any means known in the art, such as a pin, fastener,bolt, and so forth.

Referring now to FIG. 2D, telescoping column 20 and access cover 31 areomitted to reveal pneumatic unit 26. The pneumatic unit 26 includes acylinder block, as described previously, a telescoping piston rod 28that travels within the cylinder block, and a horizontal shaft 50coupled to the top end of telescoping piston rod 28 with sphericalbearing 51. The horizontal shaft 50 is carried in apertures 33 oftelescoping column 20, such that axial motion of telescoping piston rod28 is directly transferred to telescoping column 20 and test head 12. Inthe illustrated embodiment, the pneumatic unit 26 includes a brake lock630 configured to lock the position of the telescoping piston rod 28relative to the cylinder block of the pneumatic unit 26.

Referring now to FIG. 3, a cross-section of test head manipulator 16 ofFIG. 2D taken along the lines 3-3 is illustrated. As best shown in FIG.3, outer column 22 surrounds telescoping column 20, and telescopingcolumn 20 surrounds pneumatic unit 26. The piston rod 28 of pneumaticunit 26 extends from a cylindrical piston 45. The cylindrical piston 45is slideably carried within a cylinder 46 defined in the cylinder blockof the pneumatic unit 26. The vertical motion of piston 45 withincylinder 46 along axis 102 is dependent upon the axial forces acting onthe upper and lower surfaces of the piston 45. Air pressure beneathpiston 45 provides a force on piston 45 that acts in a direction to movepiston 45 upwards. Air pressure and the weight of the load acting onpiston rod 28 provides a force on piston 45 that acts in a direction tomove piston 45 down. It is noted that the weight of the load includesthe combined weights of piston rod 28, telescoping column 20, test head12, arm assembly 14, and all other apparatus attached to piston rod 28.

More specifically, the piston 45 rises within cylinder 46 if the upwardsforce due to the fluid pressure beneath piston 45 is greater than thedownwards force applied to the top of piston 45 due to fluid pressureabove piston 45 combined with the weight of the load. It follows thatpiston 45 descends within cylinder 46 along Y-axis 102 if the upwardsforce due to the fluid pressure beneath piston 45 is less than the forceapplied to the top of piston 45 due to fluid pressure above piston 45combined with the weight of the load. The piston 45 remains in asubstantially fixed position if the upwards and downwards forces onpiston 45 are substantially equal. In the exemplary embodiment theregion in the cylinder above piston 45 is vented to the outsideatmosphere; thus, the fluid above piston 45 is air maintained atatmospheric pressure. It should be understood that the fluid pressurebeneath the piston 45 is controlled and dependent upon the pressuresetting of pneumatic control unit 18. Thus, by varying the fluidpressure supplied by control unit 18, piston 45 can be controlled tomove upwards, move downwards, or remain stationary. Further, it isfeasible that additional controls may be added to the system to providecontrolled fluid pressure above piston 45, which, in certain situationsmay provide control advantages. However, for simplicity and minimum costwith reasonable performance, the described exemplary embodimentconfiguration, using air as the controlled fluid, is preferred. Theoperation of pneumatic unit 26 and pneumatic control unit 18 isdescribed in greater detail with reference to FIG. 6.

Referring still to FIG. 3, guiding member assemblies 32 are positionedon opposing exterior corners of telescoping column 20. Two guidingmembers 35 are rotatably mounted to each guiding member assembly 32.Each guiding member 35 contacts telescoping column 20 at a single point,such that each exterior side of telescoping column 20 is positionedagainst a guiding member 35. The rotatable guiding members 35frictionally engage the exterior surfaces of the telescoping conduit 20to facilitate smooth and uniform translation of conduit 20 along axis102. Furthermore, constraining all four sides of telescoping column 20(i.e., by contact with a guiding member 35) substantially limitsrotation of telescoping column 20 about Y-axis 102, and substantiallylimits both rotation and translation of telescoping column 20 about andalong the axes 104 and 106.

The guiding member assemblies 32 are mounted to opposite corners ofouter column 22. In another exemplary embodiment not illustrated herein,guiding member assemblies 32 are mounted to all four corners of outercolumn 22. However, it has been discovered that only two guiding memberassemblies 32 are required to facilitate translation of telescopingcolumn 20 along Y-axis 102, while limiting rotation of column 20 aboutaxis 102. In addition, a cost savings may be recognized by employingonly two guiding member assemblies 32 as opposed to four.

It should be understood that telescoping column is not limited to anyparticular cross-sectional shape, as the cross-sectional shape of thetelescoping column may be triangular, rectangular, square, hexagonal, orany other polygonal shape, for example, to achieve the same result.Alternatively, the cross-sectional shape of telescoping column may becircular and incorporate a slot, bend, recess, track, protrusion or anyfeature known in the art that is configured to limit rotation of thetelescoping column about its longitudinal axis. The columns 20 and 22may be formed from any rigid material, such as steel, to support theweight of test head 12 and articulating arm assembly 14.

If the cross-sectional shape of telescoping column 20 varies from theillustration, guiding members 35 may be arranged in any desired positionto complement that cross-sectional shape to facilitate translation ofthe telescoping column along Y-axis 102, while limiting rotation oftelescoping column 20 about its longitudinal axis which is parallel toY-axis 102, and limiting rotation and translation of telescoping column20 about or along the axes 104 and 106.

Although telescoping column 20 is positioned within outer column 22 inthe illustrations, the outer column 22 may be positioned withintelescoping column 20 to achieve the same benefits. It follows thatguiding member assemblies 32 may be mounted to outer column 22, asshown, or, alternatively, guiding member assemblies 32 may be mounted totelescoping column 20.

Referring now to FIG. 4, a detailed perspective view of guiding memberassembly 32 is illustrated. The guiding member assembly 32 comprises asolid block 37, and two guiding members 35 rotatably mounted to block37. The block 37 includes four threaded holes 43 for receiving fasteners41. In assembly, fasteners 41 are positioned through the wall of outerconduit 22 and threadedly fastened to threaded holes 43 for mountingguiding member assembly 32 to outer conduit 22.

In this exemplary embodiment, guiding member assembly 32 includes twoguiding members 35. The guiding members 35 are adapted to rotate freelyabout their respective axis of rotation. The guiding members 35 arepreferably cam followers but may also be casters, rings, washers,wheels, rollers, bearings or any other means known in the artfacilitating sliding motion.

The guiding members 35 are positioned substantially orthogonal to oneanother, such that the exterior corner of telescoping conduit 20 may bepositioned between the guiding members. In assembly, the revolvingsurface of each guiding member 35 is positioned to contact an exteriorsurface of telescoping conduit 20, as best shown in FIG. 3, to smoothlyguide telescoping conduit 20. It should be understood that if thetelescoping conduit 20 comprises another shape, such as a triangle, theguiding members may be positioned at other angles with respect to eachother.

As described in the Background section, the test head positionerdescribed in U.S. Pat. No. 6,888,343 includes a main arm 511 that isslideably coupled to a linear guide rail 510 that extends verticallyalong the length of column 545. A complicated and expensive motorizedpulley assembly translates main arm 511 along a Y-axis to translate thetest head 502 in the vertical direction. The weight of test head 502 issupported by a heavy counter balance 2413.

The pneumatic test head manipulator described herein represents asignificant departure from the motorized test head positioner describedin U.S. Pat. No. 6,888,343 (hereinafter '343). The pneumatic test headmanipulator described herein comprises significantly less components andweighs considerably less than the motorized pulley assembly of '343.Moreover, utilizing a plurality of guiding members provides adequateperformance and is a marked cost improvement over the expensive linearguide rail 510 and associated bearings of '343, which are commonly usedin the contemporary art of test head positioners. In contrast, guidingmembers 35 facilitate smooth and efficient translation of telescopingcolumn 20 at a considerably lower cost.

Referring now to FIG. 5, a free body diagram illustrating the forcesapplied to test head manipulator 16 is shown. The test head 12 andtelescoping column 20 are separated by a horizontal distance (alonghorizontal axis 104) by articulating arm assembly 14. By separating testhead 12 and telescoping column 20, the weight of test head 12, which isrepresented by the downward arrow 42, yields a bending moment “M” abouttelescoping column 20. This may also be commonly referred to in the artas a cantilevered load. The bending moment “M” is distributed throughthe length of telescoping column 20. The bending moment “M” producesoffsetting reaction forces 44 and 46, which are applied at the points ofcontact between guiding members 35(1) and 35(2) and telescoping column20, as shown. It follows that the guiding members 35, the fasteners thatcouple guiding members 35 to guiding member assembly 32, and thefasteners that couple guiding member assembly 32 to outer column 22, areeach uniquely designed to withstand the resultant stress of the bendingmoment “M.”

Referring to FIG. 6, an illustrative pneumatic system 600 which is partof the pneumatic control unit 18 and which is configured to control thelinear motion of the telescoping column 20 will be described. Thepneumatic system 600 is configured to control the pressure and flow offluid to pneumatic unit 26 to control the up and down motion of thepiston rod 28 as well as its static and compliant behavior. While thesystem 600 is described herein as a pneumatic system utilizing air asthe operating fluid, the invention system is not limited to such andother fluids, for example, oil, may be utilized.

In the present embodiment, the pneumatic unit 26 is a double actingcylinder which is vented to atmosphere at port 601 on one side of thepiston 45 and connected to a pneumatic feed line 603 on the oppositeside of the piston 45. A spring biased check valve 602 is provided infeed line 603 and is configured to close upon loss of pilot pressure inthe system to prevent falling of the piston rod 28. A piloted, biasedpressure regulator 604 is positioned along the feed line 603 and isconfigured to control the pressure (and consequently the rate of flow)of the fluid delivered to the pneumatic unit 26. The pressure regulator604 receives pressurized fluid from a pressure source 650 along pressurefeed line 605. A pressure regulator 648 is provided along the pressurefeed line 605 to regulate the fluid pressure to a desired pressure.Pressure regulator 648 also includes a filter (not shown) to clean theair as it enters the system.

Biased pressure regulator 604 includes a biasing member, for example, acontrol knob, to allow mechanical adjustment of the pressure and fluidflow through regulator 604 to initialize the system. The biasing membercan also be subsequently adjusted to reset the system as necessary. Thebiasing member is manipulated such that the fluid pressure passingthrough the biased pressure regulator 604 provides an upwards force onpiston 45 that is substantially equal to the downward force applied bythe telescoping column 20 and associated load on the piston rod 28. Byequalizing such pressure, the pressure on the piston rod 28 is balancedsuch that the telescoping column 20, and thereby the test head 12, is ina static or substantially weightless state. While in a weightless state,the heavy test head 12 may be manually positioned to dock (i.e., mate orengage) the test electronics of the heavy test head 12 with the IC undertest disposed on the peripheral testing apparatus 30. A pair of variablerestriction valves 607, 609 may be provided between the pressureregulator 604 and the pneumatic unit 26 to control the rate of fluidduring upward or downward movement of the piston rod 28. As described inmore detail in WO/05015245A2, due to friction and the breakaway forceassociated with piston 45, the upwards and downwards pressures acting onpiston 45 do not need to be exactly equal to maintain a static position.As is further described in WO/05015245A2, the pressure provided by thesystem may be slightly adjusted higher or lower for added systemfunctionality and capabilities.

A toggle valve 610 is provided in the pneumatic system 600 to allow anoperator to control upward and downward movement of the piston rod 28.While a toggle valve is shown and described, other types of directionalcontrol valves may be utilized. The toggle valve 610 is spring biased toa neutral position wherein a zero pilot pressure (relative toatmospheric pressure) is provided to the pilot control of the biasedpressure regulator 604. With no pilot pressure to the pilot control,biased pressure regulator 604 remains in the equalized position suchthat the piston rod 28 remains in the balanced or static state.

To move the telescoping column 20 upward, the operator moves the toggleto the ‘up’ position wherein the toggle valve 610 opens an ‘up’ pilotpressure line 611 to the pressure source 650. The pressurized fluidpasses through the ‘up’ pilot pressure line 611 to an up pilot controlof a three-position up/down valve 612, which is normally in a closedposition, and through a shuttle valve 614 to the pilot control of apilot access valve 616, which is also normally closed. The pressure onthe pilot control of the pilot access valve 616 causes the valve 616 toopen, thereby providing a fluid line 615 between the pilot control ofpressure regulator 604 and the up/down valve 612. At the same time, thepressure through ‘up’ pilot pressure line 611 onto the ‘up’ pilotcontrol of the up/down valve 612 causes an ‘up’ port of the up/downvalve 612 to open, thereby providing a direct line 613 between thepressure source 650 and the pilot control of the pressure regulator. Apressure regulator 617 is preferably provided along the pressure line613 to provide a desired positive pressure to the pilot control ofbiased pressure regulator 604. Thus, regulator 617 will control thespeed and/or the force of the pneumatic unit in the up direction.

In the present embodiment, the positive pressure to the pilot control ofbiased pressure regulator 604 causes the set pressure of regulator 604to increase, thereby increasing the pressure within pneumatic unit 26,causing the piston rod 28 and the telescoping column 20 to rise. Releaseof the toggle will return the toggle valve 610 to the neutral position,thereby discontinuing the additional pilot pressure to the pilot controlof regulator 604. As such, the output pressure of regulator 604 returnsto its original set pressure defined by the mechanical biasing memberand the piston rod 28 is again in a balanced or static state.

For clarity purposes, a brief explanation of the basic operation of thebiasing pressure regulator 604, such as the ControlAir Inc. Type 650(Positive Bias Relay) or Type 200 (Precision Air Relay), is provided.The biased pressure regulator 604 yields an output pressure that issubstantially equal to the set pressure which is the sum of the inputs,the biasing member and the pilot control member. Thus, the set pressureof the biased pressure regulator 604 can be adjusted by reducing orincreasing the force on the mechanical biasing member. In addition, theset pressure of the biased pressure regulator 604 can be adjusted byadding or subtracting pilot pressure to the pilot control member. Bothof these inputs, the biasing member and the pilot control member,provide complete control of the output pressure and can be controlledindependently. Additional information, of this type of biasing pressureregulator, including possible applications and principle of operation isavailable.

To translate the telescoping column 20 downward, the operator moves thetoggle to the down position wherein the toggle valve 610 opens a downpilot pressure line 619 to the pressure source 650. Similar to the ‘up’scenario, pressurized fluid passes through the down pilot pressure line619 through the shuttle valve 614 to the pilot control of a pilot accessvalve 616 thereby providing fluid line 615 between the pilot control ofcontrol valve 604 and the up/down valve 612. At the same time,pressurized fluid through the down pilot pressure line 619 alsoenergizes the pilot control of vacuum control valve 618 which causes thenormally closed valve 618 to open. Opening of vacuum control valve 618connects vacuum ejector 620 to the pressure source 650 via pressure line621. Again, a pressure regulator 622 is preferably provided alongpressure line 621. The positive pressure received by the vacuum ejector620 causes a negative pressure (that is, a pressure below atmosphericpressure) along pressure line 623. The pressurized fluid passing throughthe down pilot pressure line 619 also energizes a down pilot control ofthe up/down valve 612 which opens a line between the negative pressureline 623 and the pilot fluid line 615. As such, the pilot control of thebiased pressure regulator 604 is subjected to a reduced pilot pressurewhich causes the output pressure of regulator 604 to be reduced wherebythe pressure to the pneumatic unit 26 is also reduced. In other words, apressure below atmospheric pressure is applied to the pilot control ofregulator 604 which reduces its set-point pressure which in turn reducesthe pressure delivered to pneumatic unit 26. As such, the weight of thepiston rod 28, telescoping column 20 and the testing head 12 will begreater than the pressure in the pneumatic unit 26 and the piston rod 28will be lowered. Again, release of the toggle will return the togglevalve 610 to the neutral position, thereby discontinuing negative pilotpressure to the pilot control of the control valve 604. As such, theoutput pressure of regulator 604 returns to its original position andthe piston rod 28 is again maintained in a balanced or static state.

The pneumatic system 600 illustrated in FIG. 6 also includes a brakelock 630 configured to lock the position of the telescoping column 20.Brake lock 630 is controlled by fluid pressure. When no fluid pressureis applied to its inlet port, brake lock 630 is in the locked positionmaintaining telescoping column 20 in a fixed position. In order to movetelescoping column 20, fluid pressure is applied to brake lock 630. Atwo-position toggle valve 632 is positioned between the brake lock 630and the pneumatic source 650. The toggle valve 632 is normally closed sothat no pressure is applied to brake lock 630, locking telescopingcolumn 20 in position. To release the brake lock 630, the toggle isswitched to the open position such that the pressurized fluid actuatesthe release of brake lock 630. The brake lock 630 may be, for example, afluid actuated, linear rod lock. A throttle valve 634 is preferablypositioned between the toggle valve 632 and the brake lock 630 toprevent a sudden actuation of the release of the brake lock 632 when thetoggle is moved to the open position. A fluid actuated indicator 636,for example, an indicator light which lights when pressure is applied,may also be provided to indicate when the brake lock 630 is unlocked.

Referring to FIG. 7, another exemplary pneumatic system 600′ which ispart of the pneumatic control unit 18 and which is configured to controlthe linear motion of the telescoping column 20 will be described. Thepneumatic system 600′ is similar to the previous embodiment and isconfigured to control the pressure and flow of fluid to pneumatic unit26 to control the up and down motion of the piston rod 28 as well as itsstatic and compliant behavior.

As in the previous embodiment, the pneumatic unit 26 is a double actingcylinder which is vented to atmosphere at port 601 on one side of thepiston 45 and connected to a pneumatic feed line 603 on the oppositeside of the piston 45. A spring biased check valve 602 is provided infeed line 603 and is configured to close upon loss of pilot pressure inthe system to prevent falling of the piston rod 28. A piloted, biasedpressure regulator 604 is positioned along the feed line 603 and isconfigured to control the pressure (and consequently the rate of flow)of the fluid delivered to the pneumatic unit 26. The pressure regulator604 receives pressurized fluid from a pressure source 650 along pressurefeed line 605. A pressure regulator 648 is provided along the pressurefeed line 605 to regulate the fluid pressure to a desired pressure.Pressure regulator 648 also includes a filter (unnumbered) to clean theair as it enters the system.

A throttle assembly 660 is provided in the pneumatic system 600′ toallow an operator to control upward and downward movement of the pistonrod 28. The throttle assembly 660 includes a cylinder 662 with a piston664 moveable within the cylinder 662 via a handle or the like. One endof the cylinder 662 includes a port 667 open to atmosphere and the otherend includes a port 663 that is connected to a pilot line 665 fluidlyconnected to the pilot control of the biased pressure regulator 604. Avariable volume chamber 668 is defined between the piston 664 and theport 663, however, the mass of fluid, e.g. air, within the chamber 668and pilot line 665 is fixed.

The throttle assembly 660 is assembled such that when force is notapplied to the handle 666, the piston 664 is positioned such that thefluid pressure within the chamber 668 and pilot line 665 is neutral,i.e. a zero pilot pressure (relative to atmospheric pressure) isprovided to the pilot control of the biased pressure regulator 604. Withno pilot pressure to the pilot control, biased pressure regulator 604remains in the equalized position such that the piston rod 28 remains inthe balanced or static state.

To move the telescoping column 20 upward, the operator moves the handle666, and thereby the piston 664, toward the port 663, thereby reducingthe volume of chamber 668. Since the fluid mass is constant, thedecrease in volume of the chamber 668 will cause the fluid pressure inthe chamber 668 and pilot line 665 to increase. The increased pressureis applied directly through the pilot line 665 to the pilot control ofpressure regulator 604. As explained above, the set pressure of thebiased pressure regulator 604 can be adjusted by adding or subtractingpilot pressure to the pilot control member.

In the up scenario, the positive pressure to the pilot control of biasedpressure regulator 604 causes the set pressure of regulator 604 toincrease, thereby increasing the pressure within pneumatic unit 26,causing the piston rod 28 and the telescoping column 20 to rise. Theamount of increase in the set pressure of regulator 604 correlates tothe amount of additional positive pressure on the pilot control. Sincemovement of the handle 666 controls the volume of the chamber 668, theamount of increase in pilot pressure, and the corresponding increase inset pressure of regulator 604, is continuously variable over the rangeof movement of the piston 664 between the neutral position toward theport 663.

Upon release of the handle 666, the piston 664 moves back to the neutralposition to allow the pressure within the chamber 668 and pilot line 665to return to the neutral pressure.

To translate the telescoping column 20 downward, the operator moves thehandle 666 such that the piston 664 moves from the neutral position awayfrom the port 663, thereby increasing the volume of the chamber 668.Since the fluid mass is constant, the increase in volume of the chamber668 will cause the fluid pressure in the chamber 668 and pilot line 665to decrease. The decreased pressure is applied directly through thepilot line 665 to the pilot control of pressure regulator 604 whichcauses the set pressure of regulator 604 to decrease, thereby decreasingthe pressure within pneumatic unit 26. As such, the weight of the pistonrod 28, telescoping column 20 and the testing head 12 will be greaterthan the pressure in the pneumatic unit 26 and the piston rod 28 will belowered. Again, release of the handle 666 will return the piston 664 tothe neutral position, thereby discontinuing negative pilot pressure tothe pilot control of the control valve 604.

As with the up scenario, since movement of the handle 666 controls thevolume of the chamber 668, the amount of decrease in pilot pressure, andthe corresponding decrease in set pressure of regulator 604, iscontinuously variable over the range of movement of the piston 664between the neutral position away from the port 663. In both the up anddown scenarios, the variable pressure range provides a tactile feedbackat the handle 666. The operator senses that the more force the operatorapplies to the handle 666, the more the pressure will change (eitherincrease or decrease) in response thereto. This change in pressure, feltin force by the operator upon the handle 666, represents the forceapplied to the piston 45 via the biased pressure regulator 604 andthrottle assembly 660, thus providing tactile feedback. The operator canalso control the acceleration, speed, and position of the test head inthis manner. The operator may observe the movement and/or the behaviorof the test head as he or she causes the set pressure of biasedregulator 604 and thus the force on piston 45 to change via moving thehandle 666 up or down. The operator may adjust the handle 666 asnecessary to initiate motion of the test head at a desired rate,maintain a desired speed, and stop motion at a desired rate andposition.

Referring to FIG. 8, another illustrative exemplary pneumatic system600″ which is part of the pneumatic control unit 18 and which isconfigured to control the linear motion of the telescoping column 20will be described. The pneumatic system 600″ is substantially the sameas in the previous embodiment, but replaces the throttle assembly 660with a pedal throttle assembly 670, which is also continuously variableover its range of motion, provides the operator with tactile feedback,and places the operator within the motion control feedback loop.

The pedal throttle assembly 670 includes a variable volume chamber 678defined by a flexible bladder 676. The bladder 676 includes an outletconnected to the pilot line 675. One end of a foot pedal 672 ispivotally supported above the bladder 676 by a pivot junction 674. Theopposite end of the pedal 672 is desirably biased by a spring 678 or thelike to return the pedal 672 to a neutral position upon release of thepedal 672. As in the previous embodiments, in the neutral position, azero pressure is supplied to the pilot control of pressure regulator604. It is desirable that the bladder 676 is slightly precompressed inthe neutral position to provide equal up and down strokes. As indicatedin FIG. 8, applying a force to pedal 672 which compresses the bladder676 reduces the chamber 678 volume, thereby increasing the pilotpressure and causing upward movement of the telescoping column 20.Conversely, applying a force to pedal 672 which expands the bladder 676increases the chamber 678 volume which decreases the pilot pressure andcauses downward movement of the telescoping column 20.

Referring to FIG. 9, another illustrative exemplary pneumatic system600″′ which is part of the pneumatic control unit 18 and which isconfigured to control the linear motion of the telescoping column 20will be described. The pneumatic system 600″′ is substantially the sameas in the previous two embodiments, but replaces the throttle assembly660 with a plunger throttle assembly 680, which is also continuouslyvariable over its range of motion.

The plunger throttle assembly 680 includes a plunger actuated pressureregulator 682 which receives input pressure from the pressure source 650via line 681. The present plunger actuated pressure regulator 682 iscontinuously variable over a range from atmospheric pressure to apositive pressure via a plunger 684. The plunger throttle assembly 680includes a handle 686 or the like configured to engage the plunger 684.A spring 688 or the like biases the handle 686 against the plunger 684so that the plunger 684 is moved to a neutral position wherein a desiredpreload pressure flows through the regulator 682. In the presentembodiment, the biased pressure regulator 604 yields an output pressurethat is substantially equal to the set pressure which is the sum of theinputs, i.e. from the biasing member and the preload pressure. Thebiasing member is initially set taking into account the preloadpressure. The preload pressure can be any desired pressure, for example,10 psi, to provide a sufficient range of increase or decrease in the setpressure. Movement of the handle 686 toward the plunger 684 causes anincreased pressure more than the preload pressure to flow through theplunger actuated pressure regulator 682 to the pilot control of thepressure regulator 604. Movement of the handle 686 away from the plunger684 causes a decreased pressure less than the preload pressure to flowthrough the plunger actuated pressure regulator 682 to the pilot controlof the pressure regulator 604. As in the previous two embodiments, thecontrol of increased or decreased pressure is continuously variable overthe range of motion of the handle 686 and provides the operator a meansto control the vertical motion.

Referring to FIG. 10, another illustrative exemplary pneumatic system600″″ which is part of the pneumatic control unit 18 and which isconfigured to control the linear motion of the telescoping column 20will be described. The pneumatic system 600″″ is substantially the sameas in the previous embodiment, but locates the plunger throttle assembly690 along a fluid path 693 connected with the port 601 of the pneumaticunit 26 on the opposite side of the piston 45 such that the fluidcounteracts the pressure delivered to port 603 via the pressureregulator 604.

The plunger throttle assembly 690 includes a plunger actuated pressureregulator 692 which receives input pressure from the pressure source 650via line 691. The present plunger actuated pressure regulator 692 iscontinuously variable over a range from atmospheric pressure to apositive pressure via a plunger 694. The plunger throttle assembly 690includes a handle 696 or the like configured to engage the plunger 694.A spring 698 or the like biases the handle 696 against the plunger 694so that the plunger 694 is moved to a neutral position wherein a desiredcounter pressure flows through the regulator 692. In the presentembodiment, the pressure regulator 604 is configured to yield an outputpressure that is greater than the pressure required to maintain the loadin a balanced condition by an amount substantially equal to the neutralposition counter pressure. Since the neutral position counter pressureis supplied to port 601, this counter pressure counteracts the pressureprovided via regulator 604, with a resultant pressure substantiallyequal to the pressure required to maintain the load in a balancedcondition. The neutral position counter pressure can be any desiredpressure, for example, 10 psi, to provide a sufficient range of increaseor decrease in the counter pressure. Increasing or decreasing thecounter pressure from the neutral position counter pressure results inan unbalanced force upon the piston 45. Movement of the handle 696toward the plunger 694 causes an increased counter pressure, therebymoving the piston 45 down. Movement of the handle 696 away from theplunger 694 decreases the counter pressure, thereby causing the piston45 to move upward. As in the previous embodiments, the control ofincreased or decreased pressure is continuously variable over the rangeof motion of the handle 696 and provides the operator a means to controlthe vertical motion.

Referring to FIGS. 11-13, a pneumatic unit 26′ that is an alternativeembodiment of the invention will be described. As in the previousembodiment, the pneumatic unit 26′ includes a cylinder block, asdescribed previously, a telescoping piston rod 28 that travels withinthe cylinder block, and a spherical bearing 51. In the illustratedembodiment, the pneumatic unit 26 includes a brake lock 630′ configuredto lock the position of the telescoping piston rod 28 relative to thecylinder block of the pneumatic unit 26′. The brake lock 630′ is furtherconfigured to provide a pneumatic signal to the pneumatic control unit18 if the pneumatic cylinder is out of balance by more than a givenamount. The pneumatic control unit 18 may be configured to preventunlocking of the brake lock 630′ when such signal is received.

Referring to FIGS. 11-13, the brake lock 630′ includes a brake controlport 631. As in the previous embodiment, the brake lock 630′ has adefault locked position such that the lock is applied when no pressureis received through port 631. When the brake lock 630′ is switched to anunlocked position, fluid will be provided to port 631 to release thebrake lock 630′ provided an unbalanced condition is not detected asdescribed below.

In the present embodiment, the brake lock 630′ includes through passages635 which facilitate positioning of the brake lock 630′ on correspondingsupport rods 720. The support rods 720 are each secured at a first endto the cylinder block of the pneumatic unit 26′. The brake lock 630′ isaxially moveable along the rods 720 between a bottom contact plate 700and a top contact plate 710. Springs 721 or the like are positionedbetween the bottom plate 700 and the brake lock 630′ and springs 723 orthe like are positioned between the top plate 710 and the brake lock630′. The springs 721 and 723 support the brake lock 630′ for a limitedrange of motion between the plates 700 and 710. Nuts 726 or the like aresecured to the opposite ends of the rods 720 to axially secure theplates 700, 710, springs 721, 723 and brake lock 630′. The amount oftightening of the nuts 726 may be utilized to control the range ofmotion of the brake lock 630′ between the plates 700 and 710, therebycontrol the tolerance of the unbalanced signal.

As described with reference to FIG. 6 and also illustrated in FIG. 14,when the lock switch is moved to the locked position, pneumatic pressureis removed from the brake lock 630, 630′ and the lock is applied to thepiston rod 28, thereby fixing the lock relative to the piston rod 28. Inthe present embodiment, the springs 721, 723 allow the brake lock 630′to move over a limited range of motion. As such, for example, if thebrake lock 630′ is locked and thereafter additional weight or externalforce is applied on the piston rod 28, the piston rod 28, and the brakelock 630′ fixed thereto, will move against the force of springs 721. Ifthe weight or external force is sufficient, the brake lock 630′ willmove into contact with the bottom plate 700. As described hereinafter,the system is configured to provide a pneumatic signal indicating anunbalanced condition when the brake lock 630′ moves into contact withthe bottom plate 700. Similarly, if weight is removed from the pistonrod 28, the piston rod 28, and the brake lock 630′ fixed thereto, willmove upward against the force of springs 723 due to the pressure in thepneumatic unit 26. If the decrease is sufficient, the brake lock 630′will move into contact with the top plate 710. Again, the system isconfigured to provide a pneumatic signal indicating an unbalancedcondition when the brake lock 630′ moves into contact with the top plate710.

A exemplary pneumatic system 600 ^(v) configured to provide such apneumatic signal of an unbalanced condition is illustrated schematicallyin FIG. 14. The system 600 ^(v) includes a throttle assembly 660 similarto that described with reference to FIG. 7, but any up and down controlsystem may be utilized. As in the previous embodiments, pressurizedfluid is supplied from the fluid source 650 to the pressure regulator604. In the present embodiment, pressurized fluid is also provided tolock/unlock toggle valve 632.

The toggle valve 632 is normally closed so that no pressure is appliedto brake lock 630′, locking the brake lock 630′ to the piston rod 28. Torelease the brake lock 630′, the toggle is switched to the openposition. The fluid flowing through the opened toggle valve 632 flows toa detector valve 730. The detector valve 730 is spring biased to aninitial position wherein fluid travels toward a pair of sensor valves732 and 734, but not to the brake lock port 631. The fluid also travelsthrough a restrictor 634 toward an opening pilot 730 a on the detectorvalve 730. The restrictor 634 is configured to provide a sufficientdelay before the opening pilot is energized to open the detector valvefrom its initial position.

Sensor valve 732 is connected via line 733 to an inlet port 712 on topplate 710 which is fluidly connected to an open port 715 throughcompressible plug 714 extending from the bottom surface of top plate710, as shown in FIGS. 11-13. Similarly, sensor valve 734 is connectedvia line 735 to an inlet port 702 on bottom plate 700 which is fluidlyconnected to an open port 705 through compressible plug 704 extendingfrom the top surface of bottom plate 710. Each of the sensor valves 732,734 has a normally closed position such that the fluid flowing theretobypasses the valve 732, 734 and flows out the respective open port 715,705. Provided there is no back pressure, both sensor valves 732, 734will remain in such closed condition.

If an unbalanced condition exists as described above, the brake lock630′ will contact one of the plates 700, 710 and compress the respectiveplug 704, 714, thereby closing the open port 705, 715. Due to the closedport, 705, 715, a back pressure will be received at the respectivesensor valve 734, 732. The back pressure energizes the respective sensorpilot and causes the sensor valve 734, 732 to open. Fluid travelsthrough the sensor 732, 734 and actuates a respective pressure high orpressure low indicator 736, 738. The flow continues through either line737 or 739 and through a shuttle valve 740 to the maintain closed pilot730 b of detector valve 730. The force of the maintain closed pilot 730b in combination with the original spring bias of the valve 730 willmaintain the valve 730 in its initial position even upon fluid passingthrough the restrictor 634 and reaching the opening pilot 730 a. Thedetector valve 730 will remain in this initial position, and will notallow fluid to flow to the brake release port 631, until the load isbalanced, thereby uncompressing the plug 704 or 714 and removing theback pressure on the actuated sensor valve 732, 734.

The pressure high and pressure low indicators 736, 738 may be utilizedin rebalancing the load. As explained above, if the load is unbalancedwhen the toggle valve 632 is moved to the unlock position, the brakelock 630′ will not release and either the pressure high indicator 736 orthe pressure low indicator 738 will be actuated. Upon actuation, theindicators 736, 738 provide a signal to an operator that the load isunbalanced, i.e. if the load has been reduced, the pressure highindicator 736 will provide a signal and if load has been increased, thepressure low indicator 738 will provide a signal. The signals may takevarious forms, for example, an audible signal, a visual signal, or acombination thereof. In an exemplary configuration, each indicator 736,738 includes an extensible post (not shown) which is pneumaticallyextending upon actuation of the indicator 736 or 738.

The indicator signals alert the operator to the necessary pressureadjustment to rebalance the load. If the pressure high indicator 736 isactuated and providing a signal, the operator is alerted to decrease theset pressure of the biased pressure regulator 604, for example, byreducing the force on the mechanical biasing member. If the pressure lowindicator 738 is actuated and providing a signal, the operator isalerted to increase the set pressure of the biased pressure regulator604, for example, by increasing the force on the mechanical biasingmember. In an exemplary configuration, the means for increasing ordecreasing the force on the mechanical biasing member is through arotatable dial. In this configuration, the indicators 736, 738 may bepositioned relative to the rotatable dial such that the actuatedindicator 736 or 738 will guide the operator of the proper direction torotate the dial to rebalance the load. For example, if counterclockwiserotation of the dial decreases the set pressure and clockwise rotationof the dial increases the set pressure, the pressure high indicator 736is positioned to the left of the dial and the pressure high indicator738 is positioned to the right of the dial. As such, if the pressurehigh indicator 736 is actuated, the operator will know to turn towardthe indicator 736, thereby turning the dial in the counterclockwisedirection, and conversely, if the pressure low indicator 738 isactuated, the operator will know to turn toward the indicator 738,thereby turning the dial in the clockwise direction. The invention isnot limited to this configuration of the adjustment mechanism orindicators.

Once the load is rebalanced, or if the load was balanced to begin, bothports 715 and 705 will remain open and the corresponding sensor valves732, 734 will remain closed. With the sensor valves 732, 734 closed, nofluid pressure flows to the maintain closed pilot 730 b of the detectorvalve 730. As such, the fluid which flows through the restrictor 634will reach the opening pilot 730 a and provide a force sufficient toovercome the original spring bias of the detector valve 730, therebycausing the detector valve 730 to open to allow fluid to flow to therelease port 631 of the brake lock 630′. In the present embodiment,fluid also flows to an opening pilot of a throttle release valve 750.The throttle release valve 750 is positioned along the pilot line 665′and has a default closed position such that the throttle can not be usedfor up or down movement until the detector valve 730 is opened and thebrake lock 630′ released.

The illustrated embodiments show various features which may beincorporated into the pneumatic control unit 18. The invention is notlimited to the illustrated features. Furthermore, while the system isdescribed as a pneumatic system utilizing pressurized air, other fluidsmay be utilized. Additionally, while the various control systemsdescribed herein are described with respect to specific testingapparatus, the systems are not limited to such and may be utilized withany testing apparatus or load positioning apparatus, for example, butnot limited to, the apparatus described in U.S. Pat. No. 7,235,964 andco-pending U.S. application Ser. Nos. 10/567,201 and 60/903,015, each ofwhich is incorporated herein by reference. Furthermore, such controlsystems are not limited to linear actuated systems, but can be utilizedwith any load positioning apparatus, for example, rotating prime movers.

While exemplary embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those skilled in the art without departingfrom the spirit of the invention. Examples of such variations areincluded below.

The pneumatic positioner system is not limited to electronic devicetesting equipment, as other applications and industries are envisioned.The pneumatic positioner system may be utilized in X-Ray machines, orany other automated load bearing equipment. Accordingly, the term “load”recited in the appended claims is not limited to a test head, and mayrepresent any object. Also, the positioner system is not limited to airpowered pneumatics, as other power systems are envisioned such ashydraulics, motors, gears, internal combustion, etc.

Accordingly, it is intended that the appended claims cover all suchvariations as fall within the spirit and scope of the invention.

What is claimed:
 1. A load positioning system for translating a loadalong an axis of translation, said load positioning system comprising: asupport coupled to said load; a fluidly operated piston configured todrive said support along said axis of translation; a regulator unitconfigured to control a pressure of a primary fluid delivered to saidfluidly operated piston, said regulator unit receiving a first supply offluid and a second supply of fluid; and a control unit configured tocontrol a pressure of said second supply of fluid to said regulator,wherein increasing the pressure of said second supply of fluid causessaid pressure of said primary fluid to be increased and said support tomove in a first direction, decreasing the pressure of said second supplyof fluid causes said pressure of said primary fluid to be decreased andsaid support to move in the opposite direction, and maintaining thepressure of said second supply of fluid at a constant pressuresubstantially maintains the position of said support along said axis oftranslation.
 2. The load positioning system of claim 1 wherein saidsupport comprises a column.
 3. The load positioning system of claim 1wherein said support comprises a telescoping column.
 4. The loadpositioning system of claim 1 wherein the pressure of said second supplyof fluid is continuously adjustable between a maximum pressure and aminimum pressure.
 5. The load positioning system of claim 1 wherein arate of movement of said support is continuously adjustable as afunction of the pressure of said second supply of fluid.
 6. The loadpositioning system of claim 1 wherein said regulator unit is a biasedpressure regulator.
 7. The load positioning system of claim 1 whereinthe control unit includes a toggle valve moveable between up, down andneutral positions which correspond to an increase in pressure of saidsecond supply of fluid, a decrease in pressure of said second supply offluid, and a maintaining of pressure of said second supply of fluid,respectively.
 8. The load positioning system of claim 1 wherein thecontrol unit includes a throttle assembly continuously adjustablebetween a maximum pressure increase position and a maximum pressuredecrease position.
 9. The load positioning system of claim 8 wherein thethrottle assembly includes a throttle piston moveable within a throttlecylinder and having a first port vented to atmosphere and a second portin fluid communication with said regulator unit to provide said secondsupply of fluid.
 10. The load positioning system of claim 1 wherein thecontrol unit includes a pedal throttle assembly continuously adjustablebetween a maximum pressure increase position and a maximum pressuredecrease position.
 11. The load positioning system of claim 10 whereinthe pedal throttle assembly includes a flexible bladder with an outletin fluid communication with said regulator unit to provide said secondsupply of fluid.
 12. The load positioning system of claim 1 wherein thecontrol unit includes a plunger throttle assembly continuouslyadjustable between a maximum pressure increase position and a maximumpressure decrease position.
 13. The load positioning system of claim 12wherein the plunger throttle assembly includes a plunger actuatedpressure regulator with an outlet in fluid communication with saidregulator unit to provide said second supply of fluid.
 14. The loadpositioning system of claim 1 wherein the control unit includes amulti-position valve moveable between n number of positions whichcorrespond to n number of pressure increase, pressure decrease orpressure maintain positions or a combination thereof.
 15. A loadpositioning system for translating a load along an axis of translation,said load positioning system comprising: a support coupled to said load;a fluidly operated piston configured to drive said support along saidaxis of translation; a regulator unit configured to control a pressureof primary fluid delivered to the fluidly operated piston; and a controlunit configured to control a pressure of a secondary supply of fluid,wherein increasing said pressure of said secondary supply of fluidcauses an operating force at said fluidly operated piston to be modifiedand said support to move in a first direction, decreasing said pressureof said secondary supply of fluid causes said operating force to beoppositely modified and said support to move in an opposite direction,and maintaining the pressure of said secondary supply of fluid at aconstant pressure substantially maintains the position or speed of saidsupport along said axis of translation.
 16. The load positioning systemof claim 15 wherein said support comprises a column.
 17. The loadpositioning system of claim 15 wherein said support comprises atelescoping column.
 18. The load positioning system of claim 15 whereinincreasing said pressure of said secondary supply of fluid causes saidoperating force to increase and decreasing said pressure of saidsecondary supply of fluid causes said operating force to decrease. 19.The load positioning system of claim 15 wherein increasing said pressureof said secondary supply of fluid causes said operating force todecrease and decreasing said pressure of said secondary supply of fluidcauses said operating force to increase.
 20. The load positioning systemof claim 15 wherein said regulator unit is a biased pressure regulator.21. The load positioning system of claim 15 wherein the control unitincludes a toggle valve moveable between up, down and neutral positionswhich correspond to an increase in pressure of said secondary supply offluid, a decrease in pressure of said secondary supply of fluid, and amaintaining in pressure of said secondary supply of fluid, respectively.22. The load positioning system of claim 15 wherein the control unitincludes a throttle assembly continuously adjustable between a maximumpressure increase position and a maximum pressure decrease position. 23.The load positioning system of claim 22 wherein the throttle assemblyincludes a throttle piston moveable within a throttle cylinder andhaving a first port vented to atmosphere and a second port in fluidcommunication with said regulator unit to provide said secondary supplyof fluid.
 24. The load positioning system of claim 15 wherein thecontrol unit includes a pedal throttle assembly continuously adjustablebetween a maximum pressure increase position and a maximum pressuredecrease position.
 25. The load positioning system of claim 24 whereinthe pedal throttle assembly includes a flexible bladder with an outletin fluid communication with said regulator unit to provide saidsecondary supply of fluid.
 26. The load positioning system of claim 15wherein the control unit includes a plunger throttle assemblycontinuously adjustable between a maximum pressure increase position anda maximum pressure decrease position.
 27. The load positioning system ofclaim 26 wherein the plunger throttle assembly includes a plungeractuated pressure regulator with an outlet in fluid communication withsaid regulator unit to provide said secondary supply of fluid.
 28. Theload positioning system of claim 26 wherein the plunger throttleassembly includes a plunger actuated pressure regulator with an outletin fluid communication with an outlet port of said fluidly operatedpiston to provide said secondary supply of fluid to an opposite side ofan internal piston relative to the primary fluid.
 29. A load positioningsystem for translating a load along an axis of translation, said loadpositioning system comprising: a support coupled to said load; anactuator configured to drive said support along said axis oftranslation; and a fluidly operated brake lock configured tosubstantially lock the position of the actuator upon engagement of thelock, wherein the brake lock is further configured to sense when theload is unbalanced and prevent disengagement of the lock when the loadis unbalanced.
 30. The load positioning system of claim 29 wherein saidsupport comprises a column.
 31. The load positioning system of claim 29wherein said support comprises a telescoping column.
 32. The loadpositioning system of claim 29 further comprising at least one indicatorwhich indicates whether the load is balanced or unbalanced.
 33. The loadpositioning system of claim 32 wherein said at least one indicatorindicates whether an unbalanced load is based on overloading orunderloading.
 34. The load positioning system of claim 33 furthercomprising a control unit which is configured to facilitate adjustmentof an operating force on said actuator in response to an indication ofsaid at least one indicator.
 35. The load positioning system of claim 34wherein said at least one indicator indicates whether the operatingforce should be increased or decreased to balance an unbalanced load.36. The load positioning system of claim 32 wherein said at least oneindicator provides a visual indication, an audible indication or acombination thereof.
 37. The load positioning system of claim 32 whereinsaid at least one indicator includes a fluidly extensible post.
 38. Amethod of balancing a load supported on a load positioning systemcomprising a support coupled to said load; a fluidly operated pistonconfigured to drive said support along said axis of translation; and afluidly operated brake lock configured to substantially lock theposition of the piston upon engagement of the lock, wherein the brakelock is further configured to sense and indicate when the load isunbalanced and prevent disengagement of the lock when the load isunbalanced, comprising the steps of: observing an indication of anunbalanced load; and adjusting an operating force on said fluidlyoperated piston until an unbalanced load is no longer indicated.
 39. Themethod of claim 38 wherein said support comprises a column.
 40. Themethod of claim 38 wherein said support comprises a telescoping column.41. The method of claim 38 wherein the indication of the unbalanced loadindicates whether said operating force requires an increase or decreaseto balance the load.